1. Field of the Invention
The present invention relates to a method of and an apparatus for conducting a torque-down controlling of an internal combustion engine upon gear changing of an automatic transmission in a manner such that the present engine torque (an axial torque) is controlled at a predetermined demand for the rate of torque-down.
2. Background Information
As is known from Laid-open Japanese Patent Application No. 7-293682, the torque-down controlling is conducted upon gear changing by an engine control unit so that the ignition timing of an internal combustion engine is retarded in response to a demand for torque-down made by a transmission control unit.
Of recent years, in order to accomplish a further reduction in a mechanical shock upon gear changing, there has been a tendency that a delicate control is requested to be made for conducting the torque-down controlling of an internal combustion engine upon gear changing. Thus, it is necessary to conduct the torque-down controlling of the engine so that an engine toque at the present time is accurately controlled at a predetermined demand for the rate of torque-down. Nevertheless, a problem as described below occurs.
That is to say, even if a demand for the rate of torque-down against the present engine toque is determined, an angular amount that the ignition timing should be retarded cannot be definitely determined for the reason as set forth below. Namely, it is true that an engine torque can be obtained by removing a friction torque from a combustion torque of an engine. However, since the amount of friction torque changes depending on the rotating speed of the engine, an angular amount that the ignition timing should be retarded relative to a demand for the rate of torque-down must necessarily alter depending on the demand for the rate of torque-down and the engine rotating speed at that time and further the ignition timing adopted at that time. Accordingly, a lot of data must be stored, in order to accurately conduct the torque-down controlling.
A primary object of the present invention is therefore to provide a technical measure for achieving a delicate torque-down controlling according to less storage amount of data by way of such a discovery that the relationship between an amount of retard from the ignition timing for MBT and the rate of torque-down in the combustion torque can be definitely determined irrespective of the operating conditions of an internal combustion engine.
Another object of the present invention is to provide a method of controlling torque-down upon gear changing during the operation of an internal combustion, which can realize the above-mentioned primary object.
A further object of the present invention is to provide an apparatus for controlling torque-down upon gear changing during the operation of an internal combustion, which can realize the above-mentioned primary object.
In order to achieve the above objects, the present invention contrives such a technical constitution that when a torque-down controlling of an internal combustion engine is implemented at a predetermined demand for a rate of torque-down against the present torque exerted by the engine upon gear changing of an automatic transmission, the demand for the rate of the torque-down is initially converted into a rate of torque-down of a combustion torque (a desired torque-down rate), the rate of torque-down of the combustion torque is subsequently converted into a counter MBT torque-down rate that is a torque-down rate against a combustion torque at the MBT ignition timing, and further an amount of retard from the MBT ignition timing is calculated from the counter MBT torque-down rate for the purpose of achieving the torque-down controlling of the engine.
In accordance with one aspect of the present invention, there is provided a control apparatus provided to have a control communication with an internal combustion engine and an automatic transmission, and including a torque-down control unit for implementing a torque-down controlling of the internal combustion engine upon gear changing of the automatic transmission by cutting down a part of the present engine torque at a predetermined demand for torque-down rate, wherein the torque-down control unit:
converts the predetermined demand for torque-down rate into a down rate of combustion torque;
converts the down rate of combustion torque into a counter MBT down rate that is a down rate against a combustion torque at an ignition timing for a Minimum Advance for Best Torque (MBT ignition timing); and, calculates an amount of retard of ignition timing from the MBT ignition timing on the basis of the counter MBT down rate, for implementing the torque-down controlling of the engine.
In accordance with another aspect of the present invention, there is provided an apparatus for controlling a torque-down of the present engine torque of an internal combustion engine upon gear changing of an automatic transmission at a predetermined demand for a rate of torque-down, comprising:
a combustion torque down rate converting means for converting the predetermined demand for torque-down rate into a down rate of combustion torque;
a counter MBT down rate converting means for converting the down rate of combustion torque into a counter MBT down rate that is a down rate against a combustion torque at an ignition timing for a Minimum Advance for Best Torque (MBT ignition timing); and,
an ignition timing retard amount calculating means for calculating an amount of retard of ignition timing from the MBT ignition timing on the basis of the counter MBT down rate, for implementing the torque-down controlling of the engine.
In accordance with a further aspect of the present invention, there is provided a method of controlling a torque-down of the present engine torque of an internal combustion engine upon gear changing of an automatic transmission at a predetermined demand for a rate of torque-down, comprising:
converting the predetermined demand for torque-down rate into a down rate of combustion torque;
converting the down rate of combustion torque into a counter MBT down rate that is a down rate against a combustion torque at an ignition timing for a Minimum Advance for Best Torque (MBT ignition timing); and,
calculating an amount of retard of ignition timing from the MBT ignition timing on the basis of the counter MBT down rate, for implementing the torque-down controlling of the engine.
The above and other objects, features and advantages of this invention will become more apparent from the following description of preferred embodiments with reference of the accompanying drawings.